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Plug-in hybrid electric vehicles release nearly five times greater planet-heating emissions than lab-reported data show, according to a new analysis.

Growing Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs release just 19% less CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a advocacy organization. That contrasts sharply with laboratory estimates, which suggested a 75% decrease in pollution.

Analysts examined data from onboard fuel consumption monitors of eight hundred thousand cars sold in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” said a senior researcher involved in the study. “This discrepancy is growing and poses a significant problem. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Primary Reasons Behind the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery power relative to total distance. They determined that just a quarter of driving was completed in electric mode, whereas lab estimates assumed over four-fifths.

Even, when running in EV mode, emission levels were well above official projections. This occurred because EV motors were insufficiently powerful enough to function alone, resulting to engines using fossil fuels for nearly one-third of the distance completed in electric mode.

Policy and Financial Implications

Based on calculations, the lowballing of PHEV emissions allowed four major automaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 more per year in operating expenses than is estimated under lab conditions.

“The bold claims that automakers like to make about their plug-in hybrid cars are clearly far from the truth,” stated a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have recently been drawn back into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on new combustion engine cars in 2035 has faced intense lobbying from the car industry and opposition from member states with significant car industries.

Some senior officials have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the legislation.

One independent energy policy expert, who was unaffiliated with the research, described the report a “highly valuable contribution” after years in which segments of the automotive sector argued there was insufficient data to accurately evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel cars,” they said. “Any policy adjustments concerning PHEVs should be implemented with extreme care and in the light of that evidence.”